This paper investigates the effect of improper posttensioning of a 2-way spanning concrete slab subject to a central point load. Due\nto plate slippage alone, the support conditions only offered a 1-way spanning action which could have led to premature failure\nwith dangerous consequences. Posttensioning can strengthen a flat slab against punching shear by controlling deflections and\ncracking under service loads compared with traditional punching shear reinforcing methods leading to more slender structures\nand economic solutions for longer spans. However, if the method is not properly applied, these thinner floor plates can fail in a\nbrittle and sudden manner by punching at ultimate limit state and excessive deflection in serviceability. Concrete slabs containing\ntraditional shear reinforcement performed adequately and demonstrated that the critical punching shear perimeter, defined as twice\nthe depth of the slab, was confirmed from measured deflections and crack pattern analysis.
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